Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true, so safety is covered, but the description adds real behavioral context: the data source (segment notes of the annual securities report) and the not-found outcome for companies with no such customers. That not-found contract is exactly the kind of edge-case disclosure an agent needs before calling.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The lead English sentence is well front-loaded and informative, but the entire content is duplicated in Japanese, roughly doubling length. The trailing ISO 8601 date-time boilerplate is largely irrelevant to a tool whose payload is fiscal-year customer revenue, so several sentences do not earn their place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With only two parameters and no output schema, the description carries the return-shape burden and does so by listing the returned fields and the not-found case. It is nearly complete; only the relationship to sibling segment/shareholder tools is unaddressed.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100% and both parameters are documented in the schema, including the 'omit for latest annual report' behavior, so the baseline is 3. The phrase 'current and prior year' hints at the returned periods but adds no syntax or format meaning for symbol or fiscalPeriod.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description names a precise resource and scope: customers representing 10%+ of revenue, sourced from the segment notes of the annual securities report, plus the exact fields returned (name, revenue in yen, related segment, current and prior year). It is clearly distinct from siblings like get_segments or get_major_shareholders, though it never explicitly says so.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage is only implied — an agent can infer you call this when you want customer-concentration disclosure. There is no explicit when-to-use statement, no contrast with get_segments (which covers segment breakdowns) or get_major_shareholders, and no stated prerequisites.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.